In a network technology, a path computation element (PCE for short) is a centralized path computation element, which is mainly used to implement complex path computation. The PCE generally has network resource information, including a topology, a node, and a current resource usage status. A main procedure of path computation is returning, after a request from a path computation client (PCC for short) is received, path information to the PCC by using a routing algorithm and with reference to available resources of a current network. To enrich a dynamic capability of the PCE, the IETF standardization organization further extends a function of the PCE, so that the PCE can acquire a label switched path (LSP for short). A PCE of this type is referred to as a stateful PCE. In addition, an LSP Delegation function is also defined for the PCE, that is, after the PCC grants a right of modifying an LSP to the PCE, the stateful PCE may modify the LSP when necessary, and instruct a corresponding PCC to perform corresponding LSP update.
In a transport network, when a service encounters a fault, rerouting is an important means to recover the service. Rerouting indicates that available route computation is performed again according to a resource distribution situation after the fault occurs, and service transmission is recovered. In the prior art, after the fault occurs, a head node sends a rerouting request to a PCE, requesting to compute a path, without releasing an original LSP connection. The PCE recomputes the path according to resource information (including a faulty LSP). When there is a path that meets a request, a computation result is returned; otherwise, a path computation failure is returned.
However, resource utilization of a rerouting method in the prior art is relatively low. In some extreme scenarios, for example, when there are relatively few available links in the network, and no available links except an original LSP link can form a path from a head node to a last node, a path computation failure is also caused, and a service cannot be recovered.